I. Field of the Invention
The present invention relates to digital signal processing. More particularly, the present invention relates to a novel and improved apparatus and method for multiplying an analog control signal and a pulse modulated signal.
II. Description of the Related Art
Single bit pulse modulated signals are commonly used to interface digital circuitry with analog circuitry. A single bit pulse modulated signal can be the direct output of a digital circuit. The pulse modulated signal contains information in the percentage of time that the signal remains at a high logic level in comparison to the total period of the pulse modulated signal. To control analog circuitry, such a pulse modulated signal is often lowpass filtered so that the average analog value of the signal is found. The averaged analog control signal can interface directly with analog circuitry.
A need may arise to multiply a pulse modulated signal with an analog control signal. Such a need may arise when the resultant averaged analog control signal needs to vary in response to two different signals. The present invention provides an inexpensive method and apparatus to achieve the multiplication of a pulse modulated signal with an analog control signal.